Suspension system for machines



Jan. 10, 1967 N. L. PELLERlN 3,297,284

SUSPENSION SYSTEM FOR MACHINES Filed NOV. 6, 1964 3 Sheets-Sheet l INVENTOR /Vorv/'n L. Pe//er/'n ATTORNEYS Jan. 10, 1967 N. l., PELLERIN SUSPENSION SYSTEM FOR MACHINES 3 Sheets-Sheet 2 Filed NOV. 6, 1964 INVENTOR Norv/'n L. Pel/erin ATTORNEYS BY v/M/ Jan. 10, 1967 N. 1 PELLI-:RIN 3,297,284

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@5,5302 259m dm 95,62 0mm@ coroScoo 6.3i 255m f @LNH Ewwa c. f wwmEwco u .r O@ il w MA1-www5 United States Patent 3,297,284 SUSPENSION SYSTEM FOR MACHINES Norvin L. Pellerin, New Orleans, La., assignor to Pellerin Milnor Corporation, New Orleans, La., a corporation of Louisiana Filed Nov. 6, 1964, Ser. No. 409,396 Claims. (Cl. 248-18) This application relates to a suspension system for machines, and particularly for heavy duty commercial washer-extractors.

The drums of such washer-extractors rotate for a substantial portion of their cycle at washing frequencies of about 25 r.p.m., during which period the clothes tumble in the machine, striking the walls of the drum with forces thought to be as great as 3,000 pounds in a washer-extractor having a 300 lb. capacity. Since such washerextractors are ordinarily divided into three compartments these impacts occur at a frequency of 3x25, i.e., 75 times per minute.

On the other hand, such machines are usually operated at about 600 r.p.m. when water is being extracted from the clothing. The parameters and formulae for calculating the resonant frequency of a spring system for isolating such a machine (which weighs about 10,000 pounds), when operated at 600 r.p.m., are well known, and it has been found that a system having a spring rate of about 1,340 pounds per inch, an initial static deflection of about 71/2 inches, and a resonant frequency of about 70 cycles per minute is required.

Unfortunately, this is very close to the 75 per minute frequency at which the clothes strike the drum during tumbling. Moreover, when the machine is accelerated from 25 r.p.m. to 600 r.p.m. it must necessarily pass through the resonant frequency of 70 r.p.m. As it does so the amplitude of the vibrations tends toward infinity.

This disadvantage has been overcome in my system by providing means for damping the vibrations of the spring system at the resonant frequency of the system, without interfering with these vibrations at the higher frequencies occurring at extraction speeds.

This is accomplished by providing frequency responsive means controlling the ow of a shock-'absorbing fluid which is made effective to damp vibrations at the resonant frequency of a spring suspension system, but relatively ineffective at the frequencies resulting from extraction speeds.

In order that the invention may be more clearly understood one embodiment thereof will now be described, purely by way of illustration, in conjunction with the accompanying drawings, in which:

FIG. 1 is a front view of a washer-extractor embodying the invention, with parts of the pillars broken away to show two of the four shock absorbers from which the machine is suspended;

FIG. 2 is a detail View showing one of the shock absorbers, with the associated frequency responsive valve;

FIG. 3 is a detail view showing an alternative shock absorber construction; and

FIG. 4 is a graph showing the effect of frequency on the transmission of vibrations through a conventional rubber mounting.

Like reference the several views.

Turning now to FIG. 1, it will be seen that the washerextractor is supported by a framework 11 comprising four pillars 12. A combined spring and fluid shock absorber 13 is suspended from the top of each pillar by means of a ball and socket universal joint 14. The lower end of the shock absorber is attached to a ange 15, which projects from the washer-extractor at a point below its numerals denote like parts throughout center of gravity, by means of a second ball and socket universal joint 16.

Turning now to FIG. 2, it will be seen that each shock absorber 13 comprises a rod 17 attached to the pillar and a cylinder 18 attached to the washer-extractor. The lower end of the rod carries a piston 19 which slides in the cylinder, and is encircledl by a spring 20, which is compressed between the piston 19 and the top Z1 of the cylinder 18. The cylinder contains a supply of hydraulic fluid 22 which ordinarily fills the cylinder to the level L. Above and below the piston the cylinder communicates with a fluid by-pass 23, controlled by valve 24 which may be responsive to the speed of rotation of the washerextractor drum, to the frequency of the vibrations transmitted to the shock-absorber, or to the amplitude of such vibrations, so as to close when the drum turns at those speeds which cause vibrations of excessive amplitude. With the by-pass closed, movement of the piston is resisted not only by the spring 20, but by the fluid 22, in that the piston can move only to the extent that the liquid is compressed, or passes from one side of the piston to the other. The extent to which this is possible can be determined by adjusting the clearance between the piston edges and cylinder, or by providing small passages passing through the piston itself.

In fact, the by-pass may be eliminated by providing instead means for varying the clearance between the piston and cylinder in response to changes in frequency or amplitude of vibrations, or the rotational speed of the drum. FIG. 3 shows an arrangement of this type in which the periphery of the piston carries an inflatable tube 25, the rod and piston being provided with a duct 26. A valve 27 connects the duct and tube alternately to a source of compressed air or other gas and to exhaust. This valve, like the valve 24, may be responsive to the speed of the drum, or the frequency or amplitude of the vibrations, or to any other indicative parameter. Friction between the tube and cylinder wall also increases the resistance to movement by the piston when the tube is expanded.

It desired either the piston or the by-pass may be provided with a check valve 28 so that the uid is more effective in limiting movement of the piston in one direction than in the other. For instance, during the washing action it may be desirable to have the full effect of the damping to restrain the downward motion of the machine (and of the cylinder 18 relative to the rod 17) but to permit the damping uid to flow unrestrained in the opposite direction so as to permit the machine to restore itself to its proper position quickly.

The need for the present invention is graphically illustrated in FIG. 4, which charts the transmissibility of vibrations against the ratio between the frequency of the vibrations and the natural frequency of a mounting system. As clearly shown thereon the use of a resilient mounting system may be actually detrimental over a substantial range of frequencies, if no damping is provided near its resonant frequency.

It will of course be appreciated that my suspension system may be applied to machinery other than washer-extractors whenever such machinery is required to be operated at varying speeds so that it is desirable to vary the response of the suspension system in view of changes in the frequency of the resulting vibrations.

What is claimed is:

1. A suspension system for a machine which at different times during its cycle of operations generates vibrations of different frequencies, said system comprising a support, and a plurality of shock absorbers, each shock absorber comprising two relatively movable members, one of which is a cylinder and the other of which is a rod projecting from one end of said cylinder, a piston carried by said rod and slidably mounted in said cylinder, end means closing the ends of each cylinder, one of said end means being apertured to pass said rod, and spring means positioned between each piston and an end of said cylinder to resist movement of said piston in said cylinder, thereby damping vibrations of said machine, one of said relatively movable members being connected to vibrate with said machine and the other of said relatively movable members being connected to said supporting means, a uid in each cylinder, a tube connected to each cylinder on opposite sides of said piston through which said fluid may flow from each side of said piston to the other, and a valve in said tube for regulating the resistance to the ow of uid therein.

2. A suspension system as claimed in claim 1 in which the points of attachment between said machine and said one of said relatively movable members are located below the center of gravity of said machine.

3. A suspension system as claimed in claim 1 in which said relatively movable members are attached to said support and said machine respectively by means of universal joints.

4. A suspension system as claimed in claim 1 comprising means automatically restricting the flow of uid from each side of said piston to the other, in a single direction only.

5. A suspension system as'claimed in claim 1 in which said fluid is a liquid only partially lling Vsaid cylinder.

References Cited by the Examiner UNITED STATES PATENTS 872,213 11/1907 Bailey 248-18 X 1,117,057 10/1914 Korner 18S-88 1,531,938 3/1925 Hiden 248-400 X 1,766,310 6/1930 Schaum 248-18 X 3,114,705 12/1963 Pribonic et al. 248-18 X CLAUDE A. LE ROY, Primary Examrer.

2O JOHN PETO, Examiner. u 

1. A SUSPENSION SYSTEM FOR A MACHINE WHICH AT DIFFERENT TIMES DURING ITS CYCLE OF OPERATIONS GENERATES VIBRATIONS OF DIFFERENT FREQUENCIES, SAID SYSTEM COMPRISING A SUPPORT, AND A PLURALITY OF SHOCK ABSORBERS, EACH SHOCK ABSORBER COMPRISING TWO RELATIVELY MOVABLE MEMBERS, ONE OF WHICH IS A CYLINDER AND THE OTHER OF WHICH IS A ROD PROJECTING FROM ONE END OF SAID CYLINDER, A PISTON CARRIED BY SAID ROD AND SLIDABLY MOUNTED IN SAID CYLINDER, END MEANS CLOSING THE ENDS OF EACH CYLINDER, ONE OF SAID END MEANS BEING APERTURED TO PASS SAID ROD, AND SPRING MEANS POSITIONED BETWEEN EACH PISTON AND AN END OF SAID CYLINDER TO RESIST MOVEMENT OF SAID PISTON IN SAID CYLINDER, THEREBY DAMPING VIBRATIONS OF SAID MACHINE, ONE OF SAID RELATIVELY MOVABLE MEMBERS BEING CONNECTED TO VIBRATE WITH SAID MACHINE AND THE OTHER OF SAID RELATIVELY MOVABLE MEMBERS BEING CONNECTED TO SAID SUPPORTING MEANS, A FLUID IN EACH CYLINDER, A TUBE CONNECTED TO EACH CYLINDER ON OPPOSITE SIDES OF SAID PISTON THROUGH WHICH SAID FLUID MAY FLOW FROM EACH SIDE OF SAID PISTON TO THE OTHER, AND A VALVE IN SAID TUBE FOR REGULATING THE RESISTANCE TO THE FLOW OF FLUID THEREIN. 